Refrigerant scroll compressor for motor vehicle air conditioning systems

ABSTRACT

A refrigerant scroll compressor for a motor vehicle air conditioning system having a fixed scroll, an orbiting scroll engaging with the fixed scroll, wherein the fixed scroll and the orbiting scroll cooperate to compress a refrigerant gas. An intermediate pressure chamber is disposed adjacent the orbiting scroll, an oil return duct provides fluid communication between the intermediate pressure chamber and a high pressure area of the refrigerant scroll compressor, and at least one intermediate pressure duct is formed in one of the orbiting scroll and fixed scroll and is in fluid communication with the intermediate pressure chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Non-Provisional PatentApplication Serial No. DE 10 2012 104 045.1 filed May 9, 2012, herebyincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a refrigerant scroll compressor for vehicleair-conditioning systems and in this context particularly a design withefficient oil recirculation within the refrigerant circuit whilecontrolling the intermediate pressure level optimally.

BACKGROUND OF THE INVENTION

The use of refrigerant scroll compressors in motor vehicleair-conditioning systems is highly desirable, since this type ofcompressor has a robust structural design and can also be produced andused cost-effectively. Scroll compressors moreover operate radially tothe inside, which results in a relatively short axial installationlength for the compressor. An electrical refrigerant compressor can thusbe designed without requiring any additional installation space comparedto a mechanical refrigerant compressor.

The principle of compression of a scroll compressor consists of the factthat a orbiting scroll is moved in an oscillating manner within a fixedscroll such that a space forms between the flanks of the spirals, whichbecomes smaller from the external radial perimeter towards the centerand therefore compresses the refrigerant gas that was collected at theperiphery. The final compression pressure is obtained in an axial areaof the spirals and the refrigerant gas is axially discharged at highpressure. For this purpose it is important that the orbiting scroll andthe fixed scroll are sealed on their axial sides which lie one on top ofthe other, in order to prevent a radial cross flow of the refrigerantgas to the extent possible. For this reason, refrigerant scrollcompressor design principles are used, which, by forming an intermediatepressure chamber, make it possible for the refrigerant gas to act on theorbiting scroll, so that a resulting force in the axial direction iscreated, whereby the orbiting scroll is pushed against the fixed scrolland thus seals the scrolls against one another.

A known problem with refrigerant scroll compressors consists of the factthat the oil return must be designed for process safety and at the sametime must be able to develop a sufficient sealing force with referenceto the orbiting scroll by controlling the intermediate pressure.

A scroll compressor with improved oil circulation and intermediatepressure control is known from U.S. Pat. Appl. Pub. No. 2009/0191081 A1.In this context, a scroll compressor is disclosed which realizes an oilreturn via the intermediate pressure chamber towards the suction side ofthe compressor.

This design from the prior art has the disadvantage, however, that theoil return and the intermediate pressure can only be poorly controlled.

SUMMARY OF THE INVENTION

The purpose of the invention consists in providing a refrigerant scrollcompressor for motor vehicle air-conditioning systems which ensures astable oil return and where the sealing force for sealing the fixedscroll to the orbiting scroll can moreover be well controlled.

This object is solved in particular by a refrigerant scroll compressorfor motor vehicle air-conditioning systems, which comprises a fixedscroll and an orbiting scroll which rotates in an oscillating mannerrelative to same and which furthermore has an intermediate pressurechamber for generating the axial force for reciprocally sealing thescrolls. The refrigerant scroll compressor is characterized in that anoil return from the high-pressure line of the refrigerant circuit to thesuction chamber of the refrigerant scroll compressor is formed. Inaddition, an intermediate pressure duct is arranged by means of whichrefrigerant gas from the compression process between the scrolls reachesthe intermediate pressure chamber directly. The intermediate pressurechamber is therefore directly supplied with the refrigerant gas in thecompression chamber which forms between the scrolls, wherein thepressure in the intermediate pressure chamber occurs as an intermediatepressure in the respective areas of the compression chambers of thescrolls, since the pressure in the compression chamber between thescrolls in principle changes depending on the reciprocal relativemovement of the scrolls. This therefore covers an intermediate pressurerange, from which refrigerant gas flows into the intermediate pressurechamber and a resulting intermediate pressure occurs in the intermediatepressure chamber.

An advantageous embodiment of the invention consists in that the oilreturn from the high-pressure line of the refrigerant circuit is formedby means of the oil return duct to the intermediate pressure chamber andthe oil extraction duct is formed from the intermediate pressure chamberto the suction chamber of the refrigerant scroll compressor. Therefrigerant gas stream which flows directly from the compression chamberbetween the scrolls into the intermediate pressure chamber mixes withthe refrigerant oil in the intermediate pressure chamber with aresulting intermediate pressure, after which the refrigerant/oil mixtureflows via the oil extraction duct to the suction chamber.

According to another embodiment of the invention, the intermediatepressure duct is arranged in the orbiting scroll and is furthermorepreferably formed on the bottom of the orbiting scroll. It has beenshown that the intermediate pressure duct can be designed particularlycost-effectively as an intermediate pressure bore.

As an alternative to forming the intermediate pressure duct in theorbiting scroll, the intermediate pressure duct can also be arranged inthe fixed scroll, wherein the intermediate pressure duct must then beled around the orbiting scroll to the intermediate pressure chamber. Inanother embodiment, the intermediate pressure duct is arranged in thescroll such that the intermediate pressure duct is briefly within thehigh-pressure range during the compression. This means that theresulting intermediate pressure is determined essentially by theexisting suction pressure, but also by the existing high pressure. Sincethe surface which is subjected to the high pressure is essentially onthe inside of the scroll and therefore is smaller, this is accordinglyreflected thereby. As a result, an intermediate pressure results in theintermediate pressure chamber on average.

According to a further embodiment, a first expansion device is arrangedin the oil return duct and a second expansion device for restricting theoil from high pressure to the suction pressure is located in the oilextraction duct. The ratio of the cross-sections from the intermediatepressure duct to the first expansion device within the oil return ductto the intermediate pressure chamber is particularly preferable between5 and 20. Favorable results have been obtained where the ratio of thecross-sections from the intermediate pressure duct to the firstexpansion device is 10.

The relatively large flow area for the refrigerant gas compared to theflow area for the oil return results in that the resulting sealing forcecan be well controlled, and therefore it essentially operatesindependently of the oil return.

A further advantageous embodiment of the invention is realized in thatan intermediate pressure duct is formed in each of the chambers of thescroll compressor in areas which have the same functions at the samepressure level. This will increase the functional reliability of thecompressor, since if an intermediate pressure duct fails due to pluggingor the like, the lubrication still continues through the second duct.During normal operation without interference, the same lubricatingcharacteristics are obtained for both scrolls. Viewed overall, thistherefore improves the redundancy of lubricating the scrolls.

By using the conceptual implementation of the invention, thedisadvantage of the prior art of the inaccurate and complicated controland management of the intermediate pressure by a mixture of refrigerantoil and refrigerant gas by means of the oil return can be overcomeeffectively in terms of design by providing the intermediate pressureduct. Refrigerant gas flows almost exclusively through the intermediatepressure duct, and it is thus possible to obtain a stable intermediatepressure in the intermediate pressure chamber.

Various advantages result from the implementation of the principleaccording to the invention of separating the oil return and theproduction of intermediate pressure by the separate feed of refrigerantgas to the intermediate pressure chamber. It should in particular bementioned that a constant oil return flow can be guaranteed,independently of and/or less conditionally upon the intermediatepressure.

Another embodiment is that the intermediate pressure for generating theaxial sealing force between the orbiting and the fixed scroll can bewell controlled and managed. The higher intermediate pressure ensures astable sealing function during the compression of the refrigerant gasbetween the scrolls.

BRIEF DESCRIPTION OF THE DRAWINGS

Further particulars, features and advantages of the embodiments of theinvention result from the subsequent description of embodiments withreference to the associated drawings. The drawings show:

FIG. 1 is a schematic cross-section of a refrigerant scroll compressor;

FIG. 2 is a plan view of an orbiting scroll with an intermediatepressure duct, and

FIG. 3 is an embodiment of a refrigerant scroll compressor as across-section in a lateral view.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The following detailed description and appended drawings describe andillustrate various exemplary embodiments of the invention. Thedescription and drawings serve to enable one skilled in the art to makeand use the invention, and are not intended to limit the scope of theinvention in any manner.

FIG. 1 shows a highly schematic cross-section of a refrigerant scrollcompressor. For this purpose, and according to the functional principle,an orbiting scroll 2 is located in a fixed scroll 1. The orbiting scroll2 moves in an oscillating manner in the fixed scroll 1 such that betweenthe scrolls 1, 2, cavities are formed which decrease radially from theoutside to the inside, in which the refrigerant gas is compressed fromthe outside to the inside and the compressed refrigerant gas inside isfinally discharged axially into the high-pressure chamber. FIG. 1illustrates an intermediate pressure chamber 3 below the scrolls 1, 2,in which the refrigerant gas exists at an intermediate pressure. Theresulting intermediate pressure in the intermediate pressure chamber 3acts on the orbiting scroll 2 and is constituted such that a resultingaxial force results from the forces which act from the intermediatepressure chamber 3 on the orbiting scroll 2 and the opposite forcesbetween the orbiting scroll 2 and the fixed scroll 1 act oppositely. Inthe representation according to FIG. 1, the orbiting scroll 2 is pressedby the resulting axial force from the bottom against the fixed scroll 1.The orbiting scroll 2 on the side of the intermediate pressure chamber 3is sealed with respect to the stationary housing by a gasket 7.

In the fixed scroll 1 and in the housing, which is not described infurther detail, an oil return duct 4 is realized, by means of which theoil enters at a reduced flow into the intermediate pressure chamber 3from the high-pressure area of the refrigerant circuit in a firstexpansion device 5. The oil from the intermediate pressure chamber 3reaches the suction side, and/or the suction chamber of the compressor,via an oil extraction duct 6 with a second expansion device 9. Theorbiting scroll 2 is supported and sealed by means of a gasket and anO-ring on its side facing the housing.

Decisive for the functionality according to the invention is that anadditional intermediate pressure duct 8 be provided, which results inthat the refrigerant gas arrives directly at the intermediate pressurechamber 3 through the cavities which form between the scrolls, and thatan intermediate pressure results. In the illustrated embodiment pursuantto FIG. 1, the intermediate pressure duct 8 is designed for penetratingthe bottom of the orbiting scroll 2 as a bore, which directly connectsan inner area between the scrolls 1, 2 with the intermediate pressurechamber 3.

The schematically illustrated expansion devices 5, 9 are preferablycost-effectively designed as orifice plates. The principle according tothe invention of separating the oil flow from the flow of therefrigerant gas within the compression process can be realized with theillustrated embodiment. The oil return duct 4 and the oil extractionduct 6 therefore function only for recirculating the oil, whereas therefrigerant gas enters the intermediate pressure chamber 3 by means ofthe intermediate pressure duct 8 to generate the axial sealing pressure.By decoupling the oil return and the gas flow for the intermediatepressure chamber 3, the process can be controlled much more effectively.

FIG. 2 illustrates an orbiting scroll 2 and an intermediate pressureduct 8 indicated in the bottom of the scroll as an intermediate pressurebore. Intermediate pressures with a pressure ratio of 3:15 of lowpressure to high-pressure and of 5.9 to 7.6 bar can be achieved with themodified refrigerant scroll compressor. At a pressure ratio of 3:25 bar,the intermediate pressure will rise from 6.8 up to 8.6 bar, depending onhow the intermediate pressure duct 8 is positioned, and on therotational speed.

In some embodiments, the intermediate pressure duct 8 has across-section that is 10 times larger than the first expansion device 5.In this manner, the pressure in the intermediate pressure chamber 3 canbe superbly controlled by the refrigerant gas. The closer that theintermediate pressure duct 8 is formed to the inner area of the scroll,the greater is the influence at different final compression pressures.

The pressure differential between high pressure outlet and intermediatepressure results in delivering the oil through the first expansiondevice 5 into the intermediate pressure chamber 3, which is filled as aresult thereof. The pressure differential between the intermediatepressure chamber 3 and the suction area of the refrigerant compressordelivers the oil through the oil extraction duct 6 and through thesecond expansion device 9. Any oil that remains in the intermediatepressure chamber 3 flows back through the intermediate pressure duct 8into the scroll package 1, 2 to provide same with lubrication.

FIG. 3 illustrates the structural design of the refrigerant scrollcompressor a little better than a mere schematic. The refrigerant/oilmixture from the high-pressure chamber 10 of the refrigerant scrollcompressor is separated in the oil separator 11, and the liquid oilflows into the oil return duct 4 by means of a connection pipe 12. Afirst expansion device 5, designed as a restriction orifice, is arrangedupstream of the oil entry into the oil return duct 4. This decompressesthe refrigerant oil and it enters the intermediate pressure chamber 3.

Refrigerant gas from the compression process, passing from thecompression chamber 13 formed between the fixed scroll 1 and theorbiting scroll 2, enters via the intermediate pressure duct 8 into theintermediate pressure chamber 3 parallel to the oil flow from thehigh-pressure chamber 10 of the refrigerant scroll compressor. Anintermediate pressure of the refrigerant gas/oil mixture results in theintermediate pressure chamber 3.

In certain operational situations, a desirable return flow of therefrigerant oil from the intermediate pressure chamber 3 into thecompression chamber 13 occurs, as a result of which improved lubricationof the scrolls 1, 2 is achieved.

The refrigerant gas/oil mixture exits the intermediate pressure chamber3 via the second expansion device 9, which is again designed as arestriction orifice in the embodiment, and is discharged via the oilextraction duct 6.

An alternative embodiment that is not illustrated consists in that theoil return duct 4 is directed without a connection to the intermediatepressure chamber 3 directly towards the suction side of the compressor.

This form of design compared to designs from the prior art moreoverresults in a reduced number of components, and it is also possible touse standard components cost-effectively.

From the foregoing description, one ordinarily skilled in the art caneasily ascertain the essential characteristics of this invention and,without departing from the spirit and scope thereof, can make variouschanges and modifications to the invention to adapt it to various usagesand conditions.

List of Reference Symbols

-   1 Fixed scroll-   2 Orbiting scroll-   3 Intermediate pressure chamber-   4 Oil return duct-   5 First expansion device, restriction orifice-   6 Oil extraction duct-   7 Gasket-   8 Intermediate pressure duct-   9 Second expansion device, restriction orifice-   10 High-pressure chamber-   11 Oil separator-   12 Connection line-   13 Compression chamber

What is claimed is:
 1. A refrigerant scroll compressor for a motorvehicle air conditioning system comprising: a fixed scroll; an orbitingscroll engaging with the fixed scroll, wherein the fixed scroll and theorbiting scroll cooperate to compress a refrigerant gas; an intermediatepressure chamber disposed adjacent the orbiting scroll; an oil returnduct providing fluid communication between the intermediate pressurechamber and a high pressure area of the refrigerant scroll compressor;and at least one intermediate pressure duct formed in one of theorbiting scroll and the fixed scroll and in fluid communication with theintermediate pressure chamber.
 2. The refrigerant scroll compressor ofclaim 1, wherein the fixed scroll and the orbiting scroll cooperate todefine a plurality of cavities intermediate the fixed scroll and theorbiting scroll, wherein the at least one intermediate pressure duct isin fluid communication with at least one of the plurality of cavitiesand is configured to facilitate a flow of the refrigerant gas betweenthe at least one of the plurality of cavities and the intermediatepressure chamber.
 3. refrigerant scroll compressor of claim 1, furthercomprising an oil extraction duct in fluid communication with theintermediate pressure chamber.
 4. The refrigerant scroll compressor ofclaim 3, further comprising an expansion device in fluid communicationwith the oil extraction duct and disposed downstream of the intermediatepressure chamber in respect of the flow of an oil in the refrigerantscroll compressor, the expansion device configured to decompress theoil.
 5. The refrigerant scroll compressor of claim 1, wherein the atleast one intermediate pressure duct is formed in the orbiting scroll.6. The refrigerant scroll compressor of claim 5, wherein the at leastone intermediate pressure duct is an intermediate pressure bore.
 7. Therefrigerant scroll compressor of claim 1, wherein the at least oneintermediate pressure duct is formed in the fixed scroll.
 8. Therefrigerant scroll compressor of claim 1, further comprising anexpansion device in fluid communication with the oil return duct anddisposed upsteam of the intermediate pressure chamber in respect of aflow of an oil in the refrigerant scroll compressor, the expansiondevice configured to decompress the oil.
 9. The refrigerant scrollcompressor of claim 8, wherein a ratio of a cross-section of the atleast one intermediate pressure duct to a cross-section of the expansiondevice is between five and twenty.
 10. The refrigerant scroll compressorof claim 9, wherein the ratio of the cross-section of the at least oneintermediate pressure duct to the cross-section of the expansion deviceis ten.
 11. The refrigerant scroll compressor of claim 1, furthercomprising a gasket disposed adjacent the orbiting scroll configured tosupport the orbiting scroll and seal the orbiting scroll with respect toa stationary housing.
 12. A refrigerant scroll compressor for a motorvehicle air conditioning system comprising: a fixed scroll; an orbitingscroll engaging with the fixed scroll and cooperating to define aplurality of cavities intermediate the fixed scroll and the orbitingscroll, wherein the fixed scroll and the orbiting scroll cooperate tocompress a refrigerant gas; an intermediate pressure chamber disposedadjacent the orbiting scroll; an oil return duct at least partiallyformed in the fixed scroll and providing fluid communication between ahigh pressure area and a suction area of the refrigerant scrollcompressor; and at least one intermediate pressure duct formed in one ofthe orbiting scroll and the fixed scroll and in fluid communication withthe intermediate pressure chamber, wherein the at least one intermediatepressure duct is in fluid communication with at least one of theplurality of cavities and is configured to facilitate a flow of therefrigerant gas between the at least one of the plurality of cavitiesand the intermediate pressure chamber.
 13. The refrigerant scrollcompressor of claim 12, wherein the oil return duct is in fluidcommunication with the intermediate pressure chamber.
 14. Therefrigerant scroll compressor of claim 13, further comprising an oilextraction duct in fluid communication with the intermediate pressurechamber.
 15. The refrigerant scroll compressor of claim 14, furthercomprising a first expansion device in fluid communication with the oilreturn duct and disposed upsteam of the intermediate pressure chamber inrespect of a flow of an oil in the refrigerant scroll compressor and asecond expansion device in fluid communication with the oil extractionduct and disposed downstream of the intermediate pressure chamber inrespect of the flow of the oil through the refrigerant scrollcompressor, the first expansion device and the second expansion deviceare configured to decompress the oil.
 16. The refrigerant scrollcompressor of claim 15, wherein a ratio of a cross-section of the atleast one intermediate pressure duct to a cross-section of the firstexpansion device is between five and twenty.
 17. The refrigerant scrollcompressor of claim 16, wherein the ratio of the cross-section of the atleast one intermediate pressure duct to the cross-section of the firstexpansion device is ten.